1. Field of the Invention
The present invention relates to mobile communications and, more particularly, to methods and systems for communicating location in a cellular wireless communication system.
2. Description of Related Art
Cellular wireless is an increasingly popular means of personal communication in the modern world. In a cellular wireless network, a coverage area is divided into a number of sectors defined by radiation patterns from base stations. A mobile station, such as a cellular telephone, personal digital assistant (“PDA”), cellular modem, or other such device, may then communicate with the base station via a radio frequency air interface. In turn, each base station is typically coupled with other access equipment, such as a gateway or switch, to provide connectivity with a transport network such as the public switched telephone network (“PSTN”) or the Internet. A person using a mobile station can thereby communicate over the transport network from virtually any place inside the cellular coverage area.
An important feature of contemporary cellular wireless networks is an ability to locate the geographical position of a mobile station. Such a feature was initially developed to assist emergency services in locating a mobile station. For example, in the United States, the Federal Communications Commission (“FCC”) has mandated the implementation of “Enhanced 911” (“E911”) services, which includes a requirement for cellular wireless carriers to report mobile station location to a public safety access point (“PSAP”) when connecting a call from a mobile station to the PSAP.
The E911 mandate was divided into two phases. According to Phase 1, a cellular wireless carrier must identify the location of a mobile 911 caller with an accuracy of the sector in which the caller is located. According to Phase 2 (as now incorporated in Industry Standard TLA/ELA/IS-J-STD-036 (J-STD-036), entitled “Enhanced Wireless 9-1-1, Phase 2”), a cellular carrier must identify the location of a mobile 911 caller with an accuracy of at least 50 or 100 meters, depending on the mechanism used to determine location.
In order to comply with Phase 2, a wireless carrier can use network-based positioning mechanisms (such as triangularization techniques, etc.) or handset-based positioning mechanisms (such as GPS), or a combination of both. Unfortunately, however, many carriers are not yet equipped with the necessary positioning technology, and it will be some time before all or even most mobile stations are equipped with GPS positioning technology or before cellular carriers will be able to locate all mobile stations with the necessary degree of granularity.
Consequently, many carriers have focused principally on compliance with Phase 1 of the mandate.
Most carriers can readily comply with Phase 1, because a carrier usually maintains in a home location register (“HLR”) or other profile store an indication of the sector in which each active mobile station is operating. Thus, when a carrier receives a 911 call from a mobile station, the carrier can refer to the profile store in order to identify the sector where the mobile station is operating. The carrier can then set up the call to a 911 service center (as PSAP) and provide the center with an indication of that sector. Typically, the carrier will give the PSAP an indication of (i) the geographic position or street address of the base station tower and (ii) the azimuth (angle) at which the sector extends from the base station tower. Emergency service personnel can then work to locate the caller in that general direction from the base station tower.
Emergency services are thus one sort of “location-based service,” as they can use a location as a basis to provide a service. In particular, knowing the geographic location of the sector from which a mobile emergency call originates, the emergency service can seek to locate and assist the caller.
The availability of location information to support E911 services has given rise to the development of many other location-based services as well. For instance, given the location of a mobile station, a location-based service provider (e.g., a wireless cellular carrier or third party) can provide the mobile station user with a weather or traffic report in the user's vicinity. As another example, a location-based service provider can report a list of services or establishments (e.g., restaurants, parks, theatres, etc.) in the user's vicinity. As still another example, a location-based service provider can provide a mobile station user with a map of the user's location or with directions for travel between the user's location and another location. And as yet another example, knowing that a mobile station is operating in a particular location, a location-based service provider can send the mobile station a location-based message, such as an advertisement or coupon for a nearby establishment. Other location-based services exist currently or will be developed in the future as well.
Just as a cellular wireless carrier can provide a PSAP with an indication of where a mobile station is located, the carrier can provide other location-based service providers with an indication of where a mobile station is located. For instance, when connecting a call from a mobile station to a location-based service platform (or otherwise being involved with a communication session with a location-based service), the carrier can transmit to the service platform an indication of the sector in which the mobile station is currently operating. As with E911 service, the carrier might provide the geographic coordinates or street address of the sector's base station tower together with an azimuth of the sector. Alternatively, the carrier might translate the base station location into a postal zip code and report that postal zip code to the location-based service provider. The location-based service provider may then perform a service based on that location information.
When sector information has been used as a basis to describe the location of a mobile station, the description has been inherently vague, because it is not immediately clear where in the sector the mobile station is actually located. For emergency services, this presents a problem, as emergency service personnel may have trouble locating a mobile caller within a given sector. Similarly, some other location-based services may depend on knowing more precisely where a given mobile station is located, so the commercial value of those services may diminish due to the imprecision of the location information.
Therefore, a need exists for an improved method of communicating location in a cellular wireless system, so as to facilitate location-based services.